genirq: Add and use an irq_data_update_affinity helper

Some architectures and irqchip drivers modify the cpumask returned by
irq_data_get_affinity_mask, usually by copying in to it. This is
problematic for uniprocessor configurations, where the affinity mask
should be constant, as it is known at compile time.

Add and use a setter for the affinity mask, following the pattern of
irq_data_update_effective_affinity. This allows the getter function to
return a const cpumask pointer.
Signed-off-by: Samuel Holland <samuel@sholland.org>
Reviewed-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com> # Xen bits
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20220701200056.46555-7-samuel@sholland.org

arch/alpha/kernel/irq.c

@@ -60,7 +60,7 @@ int irq_select_affinity(unsigned int irq)
 		cpu = (cpu < (NR_CPUS-1) ? cpu + 1 : 0);
 	last_cpu = cpu;
 
-	cpumask_copy(irq_data_get_affinity_mask(data), cpumask_of(cpu));
+	irq_data_update_affinity(data, cpumask_of(cpu));
 	chip->irq_set_affinity(data, cpumask_of(cpu), false);
 	return 0;
 }

arch/ia64/kernel/iosapic.c

@@ -834,7 +834,7 @@ iosapic_unregister_intr (unsigned int gsi)
 	if (iosapic_intr_info[irq].count == 0) {
 #ifdef CONFIG_SMP
 		/* Clear affinity */
-		cpumask_setall(irq_get_affinity_mask(irq));
+		irq_data_update_affinity(irq_get_irq_data(irq), cpu_all_mask);
 #endif
 		/* Clear the interrupt information */
 		iosapic_intr_info[irq].dest = 0;

arch/ia64/kernel/irq.c

@@ -57,8 +57,8 @@ static char irq_redir [NR_IRQS]; // = { [0 ... NR_IRQS-1] = 1 };
 void set_irq_affinity_info (unsigned int irq, int hwid, int redir)
 {
 	if (irq < NR_IRQS) {
-		cpumask_copy(irq_get_affinity_mask(irq),
-			     cpumask_of(cpu_logical_id(hwid)));
+		irq_data_update_affinity(irq_get_irq_data(irq),
+					 cpumask_of(cpu_logical_id(hwid)));
 		irq_redir[irq] = (char) (redir & 0xff);
 	}
 }

arch/ia64/kernel/msi_ia64.c

@@ -37,7 +37,7 @@ static int ia64_set_msi_irq_affinity(struct irq_data *idata,
 	msg.data = data;
 
 	pci_write_msi_msg(irq, &msg);
-	cpumask_copy(irq_data_get_affinity_mask(idata), cpumask_of(cpu));
+	irq_data_update_affinity(idata, cpumask_of(cpu));
 
 	return 0;
 }
@@ -132,7 +132,7 @@ static int dmar_msi_set_affinity(struct irq_data *data,
 	msg.address_lo |= MSI_ADDR_DEST_ID_CPU(cpu_physical_id(cpu));
 
 	dmar_msi_write(irq, &msg);
-	cpumask_copy(irq_data_get_affinity_mask(data), mask);
+	irq_data_update_affinity(data, mask);
 
 	return 0;
 }

arch/parisc/kernel/irq.c

@@ -315,7 +315,7 @@ unsigned long txn_affinity_addr(unsigned int irq, int cpu)
 {
 #ifdef CONFIG_SMP
 	struct irq_data *d = irq_get_irq_data(irq);
-	cpumask_copy(irq_data_get_affinity_mask(d), cpumask_of(cpu));
+	irq_data_update_affinity(d, cpumask_of(cpu));
 #endif
 
 	return per_cpu(cpu_data, cpu).txn_addr;

drivers/irqchip/irq-bcm6345-l1.c

@@ -216,11 +216,11 @@ static int bcm6345_l1_set_affinity(struct irq_data *d,
 		enabled = intc->cpus[old_cpu]->enable_cache[word] & mask;
 		if (enabled)
 			__bcm6345_l1_mask(d);
-		cpumask_copy(irq_data_get_affinity_mask(d), dest);
+		irq_data_update_affinity(d, dest);
 		if (enabled)
 			__bcm6345_l1_unmask(d);
 	} else {
-		cpumask_copy(irq_data_get_affinity_mask(d), dest);
+		irq_data_update_affinity(d, dest);
 	}
 	raw_spin_unlock_irqrestore(&intc->lock, flags);
 

drivers/parisc/iosapic.c

@@ -677,7 +677,7 @@ static int iosapic_set_affinity_irq(struct irq_data *d,
 	if (dest_cpu < 0)
 		return -1;
 
-	cpumask_copy(irq_data_get_affinity_mask(d), cpumask_of(dest_cpu));
+	irq_data_update_affinity(d, cpumask_of(dest_cpu));
 	vi->txn_addr = txn_affinity_addr(d->irq, dest_cpu);
 
 	spin_lock_irqsave(&iosapic_lock, flags);

drivers/sh/intc/chip.c

@@ -72,7 +72,7 @@ static int intc_set_affinity(struct irq_data *data,
 	if (!cpumask_intersects(cpumask, cpu_online_mask))
 		return -1;
 
-	cpumask_copy(irq_data_get_affinity_mask(data), cpumask);
+	irq_data_update_affinity(data, cpumask);
 
 	return IRQ_SET_MASK_OK_NOCOPY;
 }

drivers/xen/events/events_base.c

@@ -528,9 +528,10 @@ static void bind_evtchn_to_cpu(evtchn_port_t evtchn, unsigned int cpu,
 	BUG_ON(irq == -1);
 
 	if (IS_ENABLED(CONFIG_SMP) && force_affinity) {
-		cpumask_copy(irq_get_affinity_mask(irq), cpumask_of(cpu));
-		cpumask_copy(irq_get_effective_affinity_mask(irq),
-			     cpumask_of(cpu));
+		struct irq_data *data = irq_get_irq_data(irq);
+
+		irq_data_update_affinity(data, cpumask_of(cpu));
+		irq_data_update_effective_affinity(data, cpumask_of(cpu));
 	}
 
 	xen_evtchn_port_bind_to_cpu(evtchn, cpu, info->cpu);

include/linux/irq.h

@@ -884,6 +884,12 @@ static inline struct cpumask *irq_data_get_affinity_mask(struct irq_data *d)
 	return d->common->affinity;
 }
 
+static inline void irq_data_update_affinity(struct irq_data *d,
+					    const struct cpumask *m)
+{
+	cpumask_copy(d->common->affinity, m);
+}
+
 static inline struct cpumask *irq_get_affinity_mask(int irq)
 {
 	struct irq_data *d = irq_get_irq_data(irq);